Remove unnecessary reactor reference from _PerHostRatelimiter (#14842)

Fix up #14812 to avoid introducing a reference to the reactor.

Signed-off-by: Sean Quah <seanq@matrix.org>

changelog.d/14842.bugfix

@@ -0,0 +1 @@
+Fix a long-standing bug where Synapse would exhaust the stack when processing many federation requests where the remote homeserver has disconencted early.

synapse/rest/client/register.py

@@ -310,7 +310,6 @@ def __init__(self, hs: "HomeServer"):
  self.hs = hs
  self.registration_handler = hs.get_registration_handler()
  self.ratelimiter = FederationRateLimiter(
- hs.get_reactor(),
  hs.get_clock(),
  FederationRatelimitSettings(
  # Time window of 2s

synapse/server.py

@@ -768,7 +768,6 @@ def get_replication_streams(self) -> Dict[str, Stream]:
  @cache_in_self
  def get_federation_ratelimiter(self) -> FederationRateLimiter:
  return FederationRateLimiter(
- self.get_reactor(),
  self.get_clock(),
  config=self.config.ratelimiting.rc_federation,
  metrics_name="federation_servlets",

synapse/util/ratelimitutils.py

@@ -34,7 +34,6 @@
 from typing_extensions import ContextManager
 
 from twisted.internet import defer
-from twisted.internet.interfaces import IReactorTime
 
 from synapse.api.errors import LimitExceededError
 from synapse.config.ratelimiting import FederationRatelimitSettings
@@ -147,14 +146,12 @@ class FederationRateLimiter:
 
  def __init__(
  self,
- reactor: IReactorTime,
  clock: Clock,
  config: FederationRatelimitSettings,
  metrics_name: Optional[str] = None,
  ):
  """
  Args:
- reactor
  clock
  config
  metrics_name: The name of the rate limiter so we can differentiate it
@@ -166,7 +163,7 @@ def __init__(
 
  def new_limiter() -> "_PerHostRatelimiter":
  return _PerHostRatelimiter(
- reactor=reactor, clock=clock, config=config, metrics_name=metrics_name
+ clock=clock, config=config, metrics_name=metrics_name
  )
 
  self.ratelimiters: DefaultDict[
@@ -197,22 +194,19 @@ def ratelimit(self, host: str) -> "_GeneratorContextManager[defer.Deferred[None]
 class _PerHostRatelimiter:
  def __init__(
  self,
- reactor: IReactorTime,
  clock: Clock,
  config: FederationRatelimitSettings,
  metrics_name: Optional[str] = None,
  ):
  """
  Args:
- reactor
  clock
  config
  metrics_name: The name of the rate limiter so we can differentiate it
  from the rest in the metrics. If `None`, we don't track metrics
  for this rate limiter.
  from the rest in the metrics
  """
- self.reactor = reactor
  self.clock = clock
  self.metrics_name = metrics_name
 
@@ -388,4 +382,4 @@ def start_next_request() -> None:
  except KeyError:
  pass
 
- self.reactor.callLater(0.0, start_next_request)
+ self.clock.call_later(0.0, start_next_request)

tests/util/test_ratelimitutils.py

@@ -30,7 +30,7 @@ def test_ratelimit(self) -> None:
  """A simple test with the default values"""
  reactor, clock = get_clock()
  rc_config = build_rc_config()
- ratelimiter = FederationRateLimiter(reactor, clock, rc_config)
+ ratelimiter = FederationRateLimiter(clock, rc_config)
 
  with ratelimiter.ratelimit("testhost") as d1:
  # shouldn't block
@@ -40,7 +40,7 @@ def test_concurrent_limit(self) -> None:
  """Test what happens when we hit the concurrent limit"""
  reactor, clock = get_clock()
  rc_config = build_rc_config({"rc_federation": {"concurrent": 2}})
- ratelimiter = FederationRateLimiter(reactor, clock, rc_config)
+ ratelimiter = FederationRateLimiter(clock, rc_config)
 
  with ratelimiter.ratelimit("testhost") as d1:
  # shouldn't block
@@ -67,7 +67,7 @@ def test_sleep_limit(self) -> None:
  rc_config = build_rc_config(
  {"rc_federation": {"sleep_limit": 2, "sleep_delay": 500}}
  )
- ratelimiter = FederationRateLimiter(reactor, clock, rc_config)
+ ratelimiter = FederationRateLimiter(clock, rc_config)
 
  with ratelimiter.ratelimit("testhost") as d1:
  # shouldn't block
@@ -98,7 +98,7 @@ def test_lots_of_queued_things(self) -> None:
  }
  }
  )
- ratelimiter = FederationRateLimiter(reactor, clock, rc_config)
+ ratelimiter = FederationRateLimiter(clock, rc_config)
 
  with ratelimiter.ratelimit("testhost") as d:
  # shouldn't block